Neuromuscular Research Laboratory, Department of Exercise Science and Sport Science, University of North Carolina at Chapel HillChapel Hill, NC and Human Movement Science Curriculum, University of North Carolina at Chapel HillChapel Hill, NC

Department of Nutrition, School of Medicine, University of North Carolina at Chapel HillChapel Hill, NC and Nutrigenetics Laboratory, University of North Carolina at Chapel HillKannapolis, NC

Neuromechanics Laboratory, University of KansasLawrence, KS

Neuromuscular Research Laboratory, Department of Exercise Science and Sport Science, University of North Carolina at Chapel HillChapel Hill, NC and Human Movement Science Curriculum, University of North Carolina at Chapel HillChapel Hill, NC

Methods

Fourteen NW (8 girls and 6 boys, BMI:15.8±1.4 kg/m2) and 15 OF (10 girls and 5 boys, BMI:20.8±2.3 kg/m2) children volunteered to perform this study. Percent body fat (%BF) was measured and mCSA, mEI, and subcutaneous fat (sFAT) of the vastus lateralis (VL) was assessed. MU mean firing rates (MFRs) in relation to recruitment threshold (RT) of the VL were assessed during submaximal isometric contractions. Maximal isokinetic contractions were performed at 1.05 rad·s−1 and 4.20 rad·s−1. The 95% confidence intervals (CI) from the statistical tests are presented.

Results

The OF children had greater %BF (95% CI=‐15.1 to ‐7.2), mCSA (95% CI=‐4.1 to 1.2), mEI (95% CI=‐22.3 to ‐5.9), and sFAT (95% CI=‐0.5 to ‐0.1), greater rate of strength loss with increasing isokinetic velocities (95% CI=0.4 to 5.4) and, smaller range in MFRs (95% CI=0.007 to 7.136) at the steady torque than the NW children.

Conclusions

The OF children had poorer muscle tissue composition, greater velocity‐related impairments in muscle strength, and a smaller range of MFRs at the targeted torque that may suggest altered MU recruitment strategies. Interventions in OF children should include exercises and recruit higher‐threshold MUs, such as, high‐intensity resistance exercises.